Random Formulas About Air Consumption v2

I came across a great list of formulas for helping calculate air consumption. If you have never calculated your Surface Air Consumption Rate (SAC or SCR), it is interesting to see how it varies from dive to dive. If you have an air integrated computer, this can be done for you automatically. Greg

Calculating Surface Consumption Rate (SCR) in PSI/MIN:
Salt Water: ((PSI used/Bottom Time) X 33) / Depth + 33
Fresh Water: ((PSI used/Bottom Time) X 34) / Depth + 34

Converting SCR from PSI/MIN to Cubic Feet/MIN: (note: this is how SAC or SCR is normally talked about)
Cubic Feet/min = SCR X Tank Volume (full)/Fill Pressure

Calculating Air Consumption at depth:
Air Consumption at Depth in Sea Water = Surface Consumption Rate / 33 X FSW
Air Consumption At Depth in Fresh Water = Surface Consumption Rate / 34 X FFW


Calculating how long a tank will last at depth:
Tank time = Tank Volume (cubic feet) / Air Consumption at Depth (cubic feet) OR
Tank time = Tank Pressure (PSI) / Air Consumption at Depth (PSI)